Battery fires: keeping the Li-ion caged

Lithium-ion batteries power nearly every portable device pilots and passengers carry on airplanes, and a fire sparked in an electronic device has raised concerns about the batteries’ safety.

The photo of a badly burned Apple iPhone that circulated after the phone caught fire during a Regional Express flight has raised important questions about lithium-ion battery safety among a wide aviation audience. The incident occurred after the Regional Express Saab 340B landed in Sydney, Australia, on Nov. 25, 2011, according to the airline, “when a passenger’s mobile phone started emitting a significant amount of dense smoke, accompanied by a red glow.” Although the airline didn’t identify the specific procedures the flight attendant used to contain the smoking battery, the crew “carried out recovery actions immediately and the red glow was extinguished successfully.”

The Australian Transport Safety Bureau (ATSB) provided more information, noting that the flight attendant used a fire extinguisher to cool the phone. But interestingly, this appears to be the only case in Australian aviation of a lithium-ion-powered device spontaneously combusting. According to the ATSB, “There is no previous record in the ATSB’s databases of spontaneous self-ignition involving smartphones or other portable electronic devices on an aircraft in Australia. However, the ATSB is keen to fully understand the nature of this event given the increasing and widespread carriage and use of such technology on passenger-transport vehicles.”

Lithium-ion batteries power nearly every portable electronic device that pilots and passengers carry on aircraft. “The fact that batteries can fail on rare occasions in an uncontrolled manner has brought an increased public awareness for battery safety, in particular as a result of some large product recalls of portable notebook computer and cellphone batteries,” according to a July 2011 study conducted by Exponent (Failure Analysis Associates) for the Fire Protection Research Foundation (FPRF).

Dangers of Thermal Runaway

With an energy density as high as six times that of a lead-acid battery, lithium-ion batteries are somewhat sensitive to design and manufacturing flaws. Failures are categorized as non-energetic (meaning loss of capacity, activation of a disabling mechanism, electrolyte leakage) or energetic, which is the kind that can cause smoke and/or fire. It is the energetic-type failure–thermal runaway–that most concerns flight crews.

A thermal runaway means that the battery cell releases stored energy rapidly, and lithium-ion batteries with higher energy density can release a lot more energy more quickly than other battery types. Lithium-ion batteries contain a highly flammable electrolyte, so they store both electrical energy from the normal battery chemistry and chemical energy from the lithium-based electrolyte.

Thermal runaway can occur when the battery self-heats, which can happen when electrolyte reaches temperatures as low as 158 to 194 degrees F (70 to 90 degrees C), according to the FPRF report. Runaway accelerates quickly at higher temperatures, and the greater the charge in the battery, the faster runaway happens. Temperatures during a runaway can reach 1,110 degrees F (600 degrees C). The battery cells will also experience increased pressure, venting or popping of the cell, possible ignition of cell gases, possible ejection of cell contents and propagation to adjacent cells.

According to the FPRF report, “Venting of isolated small cells (cellphone cells and smaller) seldom results in flame ignition. This is likely due to the limited volumes of vent gases released from these cells–that is, the gases become diluted before ignition can occur. In comparison, ignition of vent gases from 18650 and larger cells [used in some laptops] is fairly common: these cells contain more electrolyte (more fuel), and are usually used in multi-cell battery packs. If the flow of vent gases is ‘restricted’ due to the configuration of a vent port (typical in hard case cells), flames emanating from the cell will be highly directional (flames from 18650 cells are often described as ‘torch-like’).

“Propagation of cell thermal runaway has significant implications for fire suppression and fire protection. A fire suppressant or low-oxygen environment may extinguish flames from a battery pack, but the thermal runaway reaction will propagate if heat is not sufficiently removed from the adjacent cells. Responders to fires involving lithium-ion battery packs have often described a series of re-ignition events. Typically, responders report they used a fire extinguisher on a battery pack fire, thought they had extinguished the fire, and then observed the fire re-ignite as an additional cell vented.”

The ways that lithium-ion batteries can fail are numerous, but the report noted, “It has been observed that the vast majority of thermal runaway reactions that occur in the field occur during or shortly after cell charging.” One way of lowering risk may be to avoid charging of lithium-ion devices while in flight. It should be noted, however, that reports of spontaneously combusting lithium-ion devices that burned their owners included devices that were not being charged.

Anyone flying with lithium-ion-powered devices might want to know of these hazards and take steps to minimize the risk of a thermal runaway from an onboard device, especially now that many pilots have adopted tablet computers for chart and document viewing.

Fire-Containment Options

The FAA highlighted lithium-ion problems and strategies for dealing with lithium battery fires in a Safety Alert for Operators (SAFO 09013). The FAA recommends: “Utilize a Halon, Halon replacement or water fire extinguisher to prevent the spread of the fire to adjacent battery cells and materials. Pour water, or other non-alcoholic liquid, from any available source over the cells immediately after knockdown or extinguishment of the fire.” The idea is to cool the battery to prevent re-ignition and propagation to other cells. While water reacts with lithium, the amount in the electrolyte is sufficiently small that it is worth the cooling effect of the water when trying to stop the runaway, according to the FAA.

Lithium-ion batteries are often encased in hard plastic shells, however, and this hampers efforts to drown a lithium fire with water, according to Tom Connolly, president of Industrial Fire Products, Mount Joy, Pa. Connolly’s company manufactures the Fire-Fighter Hot-Stop L fire-containment bag that Ship-it AOG distributes. The problem with water, he told AIN, is that it can’t penetrate the plastic case around a battery and won’t put out the fire until the case fails fully, by which time the thermal runaway has proceeded nearly to conclusion, generating high temperatures. Placing the burning device in the Hot-Stop bag contains the thermal runaway safely as the fire burns itself out. The bag does not snuff out the fire, he pointed out. “From the flight crew standpoint, is it better to package a passenger’s device [into the containment bag] that is running hot or smoking or to begin pouring water on it that cannot penetrate the battery casing yet? The feedback we receive is that they want the item in question contained now, guesswork eliminated and the ‘event’ contained.”

The Hot-Stop bag, available in two different sizes, is made of materials with a melting point of 3,200 degrees F (1,760 degrees C). It includes a set of heavy-duty firefighter gloves to protect the crew dealing with the burning device. The large Fire-Fighter bag sells for $1,075 and the smaller Fire-Fighter II bag sells for $950. Both are available from Ship it AOG.

Aircare Access Assistance offers a fire-containment bag, the FireSock, which sells for $339, including gloves. Aircare recommends stopping the thermal runaway first using Halon or water, then putting the device into the FireSock. If no water or Halon is available, Aircare suggest putting a burning device in the FireSock.

Another company, FCB 1200, developed a fire-containment bag three years ago, and president Randy Steenholdt worries that the FAA is not considering the many laptops with magnesium frames flying on long overwater or remote routes without any protection other than Halon and water. “If magnesium catches fire, it will keep burning,” he warned. Steenholdt recommends keeping laptops carried in cabins in containment bags as a precaution, especially on Etops trips. An in-flight fire stemming from lithium laptop batteries is inevitable, he believes, and when a tragedy happens, “the FAA will finally react.”

In considering the hazards of lithium batteries, one message comes through loud and clear: you’ll be much happier when you carry some kind of bag to isolate and contain a lithium-battery-powered device that spontaneously overheats or bursts into flame. While spontaneous combustion of lithium battery-powered devices doesn’t seem to happen that often, a fire-containment bag will help keep the fire from spreading into an all-out disaster.

Comments

Jim Bynum (not verified)

February 7, 2012 - 3:34pm

In looking for an common denominator in the Li-Ion battery problems:

Is there information available that would reveal if the batteries presenting problems are cheap replacements or if the OEM batteries were past a certian age or if they had been damaged in any way or charged improperly?

Having had a >1 year old phone pack "vent with flame" when overcharged then triggered internal short, I can appreciate this issue.
Especially dangerous are recalled packs that have not yet been dealt with, or ones where the cell(s) have been overdischarged then recharged badly as happens with cheap MP3/DVD players.

Should there be a list of known recalled packs, with serial numbers at the gate?
Would reduce the risk of an in flight fire somewhat, however the main problem is that in a lot of cases the pack can be dangerously unstable due to ageing yet still work "well enough" i.e. 75% capacity.

Seems that copper shunt formation is also a big problem in old packs, as many R/C enthusiasts know to their cost.
For once, a "warranty timer" might be a safety critical feature even though it would annoy a lot of people it could save lives.

My partner got an Apple iPhone 5 some time back and gave me the Richard Solo Power Skin battery pak he had previously used with his iPhone 4. Now I have been using it with my iPhone for some months. On February 7, 2013 I was having lunch at my local Deli hangout and thought I felt my phone buzz indicating an incoming call. I put my hand into my pants pocket to retrieve the phone but noticed the pocket was hot and smoke was pouring through the fabric and out of the pocket. I started to run to the bathroom to remove my pants and retrieve the phone but others in the restaurant feared I didn't have time and began pouring water on me and even a pitcher of iced tea into the smoking pocket. When I finally reached the bathroom the Richard Solo device had burned through my pocket and through my underwear and into my thigh. The device was melted and deformed. The iPhone fell to the floor as I tried to get rid of the fire hazzard and the corner of the glass face broke but otherwise it was not physically changed by the fire although I assume the water used to put out the fire is what has destroyed its function. I notified Richard Solo company about the incident and injury and provided all numbers and other identification from the device but their response was that they could offer me no help despite my burns, my burned pants and underwear, my lost battery pak and my lost iPhone 4S unless I provided them with the order number for the device which my partner no longer has. So until a personal injury attorney obtains other relief all I can do is post this notice that spontaneous combustion of the Richard Solo Power Skin is certainly possible and the resulting burn is certainly painful.